Define what is Physics

Alternative definitionof Physics the study of matter and energy. the science of matter and energy and theirinteractions Physics (from the Greek, (phusikos),"natural", and (phusis), "nature") is thescience of Nature in the broadest sense. Physicistsstudy the behavior and properties of matter in awide variety of contexts, ranging from the subnuclear particles from which all ordinary matter ismade (particle physics) to the behavior of thematerial Universe as a whole (cosmology).

Defining Physics The word physics is derived from Greek word fusis,meaning nature or natural things. As such, physics isdefined as that branch of science, which studies naturalphenomena in terms of basic laws and physical quantities. The study is generally structured to satisfy queries, arisingfrom the observed events occurring around our world. In thissense, Physics answers questions about universe and theway elements of universe interact to compose naturalphenomena. The underlying principles in physics are simple and general,but defining (basic) in nature. Elements and quantities usedto describe natural phenomena are also general and basic.The whole of universe, matter of fact, can be considered tobe comprising of two basic quantities : (i) matter and (ii)energy. For this reason, some physicists rightly definephysics as the study of matter and energy.

Domain ofphysics extends from infinitesimal toinfinite and is largelyundefined. At one end ofscale, there are quarkscomposing nucleons(neutrons and protons) andon the other end, there isgalaxy, comprising of sun likestars as its constituents andan universe that we do notknow much about.

In physics, domains are also defined in terms of various

important attributes like speed, temperature and otherphysical quantities. In the domain defined by speed, westudy both stationary objects and objects moving at veryhigh speed, may be three fourth of the speed of light.Thanks to the extraordinary efforts of scientist in the lasttwo centuries that we, now, know of some of the importantbounds of nature. For example, upper limit of speed is thespeed of light. Similarly, lower limit of temperature is 0 K.These are some of the highlights of the development in thebasic understanding of nature and its extent. The uncertainty about domain of physics stems from thefact that new experiments and discoveries continuouslybreak the bounds (limits) set before. For some time, thecharge on electron was considered as the basic or smallestlump of charge, but today after the discovery of quarks, weknow that quarks carries lesser amount of charge than thatcarried by electrons. Thus, extent of physics is actuallychanging as we learn more about nature.

Generality

Theories of physics are extremely general, being the

underlying governing principles of natural eventsextending to the whole universe. This aspectcontrasts physics from other streams of science,which are often specific and sometimes localized.Generality of physics and its theories render physicallaws to form the basic scientific framework uponwhich other braches of science are developed. Takethe example of ions constituting a molecule - asubject of investigation in Chemistry. The ions are,however, glued together under the influence ofelectrostatic force irrespective of the nature and typeof ions and molecules involved. The magnitude ofthis electrostatic force is secular in that its magnitudeis determined by inverse square law whatever bethe context and location.

implification and unification

Simplification and unification have emerged as the basictrait of physics. There are only few laws to define widevariety of natural phenomena a fact that underlines thesimplification of governing laws in physics. On the other hand, unification of physical quantities /concepts is also prevalent. Take the example of matter andenergy. They are now considered equivalent. Special theoryof relativity establishes equivalence of two quantities as

E=mc2

Further, dual nature of matter highlights wave (energy)

nature of particle (mass), which reinforces the concept ofmass-energy equivalence. Similarly, treatment ofmagnetism in terms of electrical charge is an example ofunification of physical concepts.

Simplification and unification can also be seen in the laws

governing gravitation and electrostatics. Gravitational and electrical forces are conservative forces,determined by inverse square laws. The similarity of theforms of mathematical expressions is no coincidence, but asure indication of the underlying nature of the universe,which emphasizes simplification : Gravitation Force

Electrostatic Force

Simplification and unification of physical quantities, concepts

and laws are remarkable, suggesting more such cases which are yet to be discovered. Consider the physicalquantities : mass and charge. There is yet no relationshipconnecting these two fundamental quantities of physics.Similarly, two major categories of forces known as nuclearand weak forces are not yet fully understood. Scientists areworking to examine these unknown territories.

Scientific validation and

experimental Verification The fundamental laws of physics are setagainst either too big or too small quantities,presenting a peculiar problem in establishingdirect validation of basic theories in physics.Even today, there is not a single experimentalset up which could directly verify Einsteinstheory of relativity.

Scientific validation and

experimental Verification

For example, mass of an electron moving at two

third of the speed of light can not be measureddirectly. As we do not see atoms and itsconstituents, theories based on them are also notdirectly verifiable. We can not even verify Newtonsfirst law of motion, which states that an object inthe absence of net external force shall keepmoving! We have seen all objects come to rest inthe earth's frame of reference, when left unaided.This peculiarity, however, does not mean thatthese laws have not been validated as required forscientific studies. It should be amply clear that scientific method forvalidation also includes inferences based onindirect measurements. In that sense, Einsteinsspecial theory of relativity has been tested andverified by results obtained from the experimentsinvolving motions of charged particles at greatspeed. Surprising is the exactness and accuracy ofthe results obtained. In the same context, accuracyof predications involving solar systems, satellitesetc. have validated laws of gravitation.

Recasting and revalidating laws

in the light of new revelations Studies and experiments continue to bring new details anddimensions to our understanding of natural phenomena. New revelations recast old facts, hypotheses and theories. The relativity theory propounded by Albert Einstein, forexample, revealed that Newtons laws of motions arebasically a subset of more general theory. Similarly, Newtonshypothesis regarding velocity of sound was recast byLaplace, arguing that propagation of sound is adiabatic andnot isothermal process as considered by Newton. His assertion was based on the experimental result and wascorrect. There are many such occasions when an incomplete orerroneous understanding of natural event is recast orvalidated when new facts are analyzed.